Robust adaptive error control

This paper presents a robust adaptive type-I hybrid ARQ scheme that can adapt to a slowly-varying wireless channel. The proposed system can improve system throughput substantially compared to a conventional type-I hybrid ARQ scheme. Most previous research on adaptive ARQ has assumed that the return channel used for acknowledgements is error free. This simplifying assumption is often necessary for initial performance evaluation but is unrealistic in practice. In this paper, we extend an existing adaptive ARQ scheme by making it robust to channel errors in both the forward and feedback channels. We also propose a solution to maintain code synchronization in the presence of packet errors and describe an implementation that combines the adaptive ARQ scheme with a SACK protocol that allows bi-directional transmission and piggybacked acknowledgements. In addition we have built a wireless test platform for mobile radio in an attempt to accurately measure the adaptive error control performance not only as a standalone entity, but also as a part of a complete protocol stack